Because of wide variations which occur in crops which are harvested, a need has been recognised for an indicator which will indicate the grain loss.
When a crop is harvested, the stalk and heads are cut off at about mid length, and fed into a thresher. The husks are blown out by a fan situated beneath the thresher. If there is too much draft the fan will cause excessive quantities of grain to be blown out with the husks. Straw is also thrown onto the straw walkers of the combine, and the straw walkers carry the straw to the back of the machine and on the ground. If there is too much intake by the machine for the capacity of the thresher, the thresher becomes overloaded and does not fully thresh all the heads of the stalks, and this also leads to grain loss along with the straw as it is discharged from the walkers.
This problem has been recognised, and in the U.S. Pat. No. 3,593,720 to J. R. Botterill and U.S. Pat. No. 3,606,745 to J. C. F. Girodat, grain loss monitors were disclosed which were arranged to detect the number of grain kernels passing per unit of time at the discharge end of the walker or the sieves. There have been developments on these early Patents, and in the U.S. Pat. No. 3,939,846 to Drozhzhin et al. there was described a device which included a transducer for measuring the amount of grain lost by the thresher and a transducer for measuring the amount of grain supplied to the hopper, the outputs of the transducers being connected to a ratio detector. In the device of Kirk, U.S. Pat. No. 4,004,289 there was described a device wherein chaff impinged upon a sensor to provide a signal which passed through two or more band pass filters centred at predetermined frequencies. In the U.S. Pat. No. 3,935,866 et al, (assigned to Allis-Chalmers Corporation) there was described a device wherein a monitor derived a grain loss rate signal which was in accordance with the number of grains impinging on a transducer, and this was related to a ground speed signal to provide a reading of percent grain loss per acre.
With all the prior art specified above, and otherwise known to the Applicant, there has been a basic problem which has not been overcome heretofore. Under main circumstances of use, the grain impinging on the sensor is associated with relatively large quantities of chaff or straw, and accurate readings of loss are difficult to achieve. The main object of this invention therefore is to provide a simple grain loss indicator wherein the sensor is more sensitive to the grain content of discharged discrete material than has been achieved heretofore.